1. Field of the Invention
The present invention relates generally to apparatus and methods for endoluminal placement of grafts, stents, and other structures. More particularly, the present invention relates to a low profile, compressible graft structure and apparatus and methods for vascular placement of such structures for the treatment of abdominal and other aneurysms.
Vascular aneurysms are the result of abnormal dilation of a blood vessel, usually resulting from disease and/or genetic predisposition which can weaken the arterial wall and allow it to expand. While aneurysms can occur in any blood vessel, most occur in the aorta and peripheral arteries, with the majority of aortic aneurysms occurring in the abdominal aorta, usually beginning below the renal arteries and often extending distally into one or both of the iliac arteries.
Aortic aneurysms are most commonly treated in open surgical procedures where the diseased vessel segment is bypassed and repaired with an artificial vascular graft. While considered to be an effective surgical technique, particularly considering the alternative of a usually fatal ruptured abdominal aortic aneurysm, conventional vascular graft surgery suffers from a number of disadvantages. The surgical procedure is complex and require experienced surgeons and well equipped surgical facilities. Even with the best surgeons and equipment, however, patients being treated frequently are elderly and weakened from cardiovascular and other diseases, reducing the number of eligible patients. Even for eligible patients prior to rupture, conventional aneurysm repair has a relatively high mortality rate, usually from 3% to 10%. Morbidity related to the conventional surgery includes myocardial infarction, renal failure, impotence, paralysis, and other conditions. Additionally, even with successful surgery, recovery takes several weeks, and often requires a lengthy hospital stay.
In order to overcome some or all of these drawbacks, endovascular graft placement for the treatment of aneurysms has been proposed. Although very promising, many of the proposed methods and apparatus suffer from other problems. Often times the proposed graft structures will have exposed anchors or frame which can be thrombogenic. It is also difficult to provide graft structures which remain sealed to the blood vessel lumen to prevent the leakage or bypass of blood into the weakened aneurysm, especially when subjected to external deforming forces which result from vessel expansion and contraction as the heart beats. Many vascular graft structures have difficulty in conforming to the internal arterial wall, particularly since the wall can have a highly non-uniform surface as a result of atherosclerosis and calcification and is expanding and contracting with the patient's heartbeat and blood flow. Additionally, many previous vascular graft structures are difficult to position and anchor within the target region of the vessel.
For these reasons, it would be desirable to provide improved apparatus and methods for the endovascular placement of intraluminal grafts for treating aneurysms and other conditions. It would be particularly desirable if the graft structures were easy to place in the target region, displayed little or no thrombogenicity, provided a firm seal to the vascular wall to prevent leakage and blood bypass, and were able to conform to uniform and non-uniform blood vessel walls, even while the wall is expanding and contracting with the patient's heartbeat.
2. Description in the Background Art
Vascular grafts and devices for their transluminal placement are described in U.S. Pat. Nos. 5,219,355; 5,211,658, 5,104,399; 5,078,726; 4,820,298; 4,787,899; 4,617,932; 4,562,596; 4,577,631; and 4,140,126; and European Patent Publications 508 473; 466 518; and 461 791.
Expandable and self-expanding vascular stents are described in U.S. Pat. Nos. 5,147,370; 4,994,071; and 4,776,337; European patent Publications 575 719; 556 850; 540 290; 536 610; and 481 365; and German patent Publication DE 42 19 949. A flexible vascular stent structure having counter wound helical elements, some of which are separated at particular locations to enhance flexibility, is commercially available from Angiomed, Karlsruhe, Germany, as described in a brochure entitled Memotherm Iliaca Stents.
Catheters for placing vascular stents are described in U.S. Pat. Nos. 5,192,297; 5,092,877; 5,089,005; 5,037,427; 4,969,890; and 4,886,062.
Vascular grafts intended for open surgical implantation are described in U.S. Pat. Nos. 5,236,447; 5,084,065; 4,842,575; 3,945,052; and 3,657,744; and PCT applications WO 88/00313 and WO 80/02641; and SU 1697787.
Nickel titanium alloys and their use in medical devices are described in U.S. Pat. Nos. 4,665,906 and 4,505,767.